libmstpm: compile openssl with -O3 for release build

[cclaudio]

As mentioned in the merged PR #317, the openssl fails to compile when we pass any optimization to gcc (e.g. -O3). However, ideally make RELEASE=1 should build it passing -O3. We could use other platforms as reference, the upstream openssl config files show some platforms passing -O3 to the compiler.

In the last SVSM meeting, we discussed that one option could be:

• keep the no-sse2 parameter in the openssl Configure cmd-line
• rather than passing the CFLAG -mno-sse, implement handlers in the SVSM to mitigate the unhandled exception 6

[joergroedel]

The right fix for this is to enable FPU usage in the SVSM code base. This will be needed anyway as user-mode support progresses. @vsntk18 volunteered to look into this.